I'm preparing to record a new instructional video explaining the different sizes and ranges of missiles and the launchers that fire them. However, I've noticed an oddity with Rapid Torpedo Launchers that I can't understand.

Rapid Light Missile Launcher Is have slightly less than half the refire cycle time of Light Missile Launcher Is (7.8 seconds versus 16 seconds, before skills and bonuses). Similarly, Rapid Heavy Missile Launcher Is have much less cycle time than Heavy Missile Launcher Is (6.48s vs. 15s). However, comparing Rapid Torpedo Launcher I to Torpedo Launcher I goes against this trend (28.45s vs. 18s).

I have noticed that both variants of the Siege Module (used by the Phoenix Dreadnought) multiply the refire time by 0.2 and that the Leviathan Titan has a 15% bonus-per-level to reduce the refire time.

So, my question is this: are Rapid Torpedo Launchers intended to be useless on a Phoenix without Siege mode?